Electron discharge device



June 26, 1962 L. FElNSTElN ET AL ELECTRON DISCHARGE DEVICE Filed Aug.30, 1950 II/IIIIIIII)"IIIpVIII/III 'IIIIIIII 'IIIA-Ill INVENTORS. LESTERFEINSTEIN B MORTIMER E.WEISS fl 142 EY rates United The presentinvention relates to electron discharge tubes and more particularly toan improved form of construction of such tubes.

An object of the present invention is to simplify the construction ofelectron discharge devices.

Another object of the present invention is to utilize the elementspacers of the amount of an electron discharge device as part of theevacuated envelope of the device.

Another object :of the present invention is the provision of a form ofconstruction for electron discharge devices in which there is providedcomplete peripheral support of the elements which cooperate with theelectron stream.

Still another object of the present invention is to increase thestructural rigidity of an electron discharge dev1ce.

In most conventional vacuum tube constructions with which we arefamiliar, the grid or grids and anode of the tube may be supported atone or both ends by leads or eyelets which are inserted in mica spacingwashers in order to provide a unitary mount assembly. The mount assemblyis then secured to a stem or header at one end of the tube. Thus ingeneral, the entire mount may be considered to be supported at one endby the stem or header and at the other end by the mica spacer which maybe entirely free of the envelope or may be to some extent supported bycontact with the envelope. In order .to allow for some variation inenvelope dimensions the spacer may be provided with points which aredeformed by contact with the envelope wall to provide a snug fit ormetal spring members may be secured to the mica for the purpose ofcontacting the envelope. Due to the inherent fragility of mica, a secureand rugged support for the mount is not thus obtained. Alternate knownforms of tube construction may employ disc-like anode and grid elementssealed between sections of glass tubing. However, such construction, inaddition to being expensive and difiicult to fabricate, does not providefor accurate dimensioning of the space between elements and is notcharacterized by extreme ruggedness.

Further objects, therefore, of the present invention at .to overcome thedisadvantages of previously known vacuum tube constructions which areset out above. q

The foregoing objects as well as additional objects which may appear inthe following description as it proceeds, are attained in accordancewithan aspect of the present invention by providing grid and anodestructures which are, or form part of,.metallic disc-like elements whichare supported around their entire periphery by being soldered or brazedto a ceramic ring spacer interposed between the grid andplate discs. Theceramic ring also forms a part of the vacuum enclosure or envelope ofthe tube. .7 I i The present invention employs a ceramic ring ratherthan glass because ceramics are inherently dimensionally stable underthe high temperatures necessary to join the various parts of the tube tomake a completed unit. To the side of the grid disc opposite the ceramicspacer ring is welded, brazed or otherwise hermetically secured, a metaleyelet, in the form of a hollow, metallic cylinder having an outturnedflange at one end which is secured to the grid disc. The hollow,cylindrical eyelet is hermetically sealed at a point remote from theoutturned flange by means of a glass plug secured within the eyelet. A

atent O number of lead-in conductors pass through the glass plug and totheir inner ends are secured supports for the cathode, whether it be afilamentary cathode or an indirectly heated solid cathode. The cathodesupport preferably includes mica spacer elements which engage slots inthe grid disc and have shoulders which press against the lower side ofthe grid disc and thus accurately space the cathode from the grid.

The form of our invention described above utilizes the cylindrical shellor eyelet as a means for connecting to the control grid. If desired, anadditional ceramic ring may be interposed between the grid disc and themetal shell so as to provide a separate connection for the grid. Theshell may then be connected internally to the cathode to form thecathode connection or it may be employed purely as a shield connectionand a separate lead through the glass plug employed for the cathodeconnection. In the form of the invention described above, themetal-toceramic seals are made between the directly contacting edges. Insome cases a variation in the amount of brazing material between theceramic ring and the metal discs mayunfavorably aifect the spacingbetween the electrodes within the tube. A modification of our invention,therefore, may utilize a ceramic ring which is H-shaped in cross sectionwith the dimension of the heighth of the H being accurately determinedby grinding to a predetermined size. The anode disc and the grid dischave flat portions which lie against the accurately ground ends of thering and turned over portions or lips which dip into the channels of theH and are sealed therein by brazing material melted into the channels.

The present invention will be more fully understood by reference to thefollowing detailed description which is accompanied by the drawing inwhich- FIGURE 1 shows in vertical cross section an embodiment of thepresent invention while FIGURE 2 shows a vertical cross section of amodified form of the invention and FIGURE 3 is a vertical section of theform of the invention shown in FIGURE 2 taken along a vertical plane atright angles to the cutting plane of FIGURE 2 while FIGURE 4 is ahorizontal section taken along line 4-4 of FIGURE 2 p FIGURE 5 is ahorizontal cross section taken along the line 55 of FIGURE 2 and FIGURE6 is a vertical section similar to FIGURES l and '2. of a modified formof the invention.

FIGURE 1 shows an anode disc 10' which may have a central dished-inportion 11 so dimensioned as to fit within the central aperture of .aceramicring 12. A second disc 1-4, having a central aperture 15 thereinacross which grid wires '16 are stretched to form a grid electrode, isdished similarly to anode disc10 and adapted to be brazed or otherwisesecured to the opposite face of ceramic ring 12. To the opposite face ofgrid disc 14 is secured the flange 17 of a hollow, metallic cylinder oreyelet 18, within which is sealed a glass header disc 20, through whichpassa number of lead-in conductors 21. The inner ends of lead-inconductors 21 carry, by appropriate fastening means, mica cathodesupporting plates 22, 24 which as shown better in FIGURE 3, have, alongtheir upper edges, a pair of notches 25 in whichfthe filamentary cathodewire .26 rests, The mica plate in the space between notches v25 ispreferablyrextended upwardly in the for-mof a tongue 27 which is sodimensioned in width and length as to tightly fit within notches 28 and29' at the ends of the grid disc aperture 15.(FIG. 5).

From a consideration of FIGURE 3 it will be seen that thetop edges ofthe mica spacers 22 and 24 rest against ,assembly may be made in abell-jar spring, while the base of the T is secured to the support forthe mica spacer 24. The free ends of the filament are preferablyconnected to the adjacent pair of lead-in conductors 21 at the outerside of mica spacer 22.

In fabricating a tube according to the present invention,

a subassembly, including the metal eyelet 18, the header disc 20 and thefilament support and spacer assembly is suitably secured on a temporarysupport which is adapted to be placed within a bell jar which may beevacuated. The grid disc 14, the ceramic ring 12 and the anode disc 10are positioned on top of rim 17 of eyelet 18 with thin rings of abrazing alloy interposed between adjacent surfaces. The bell jar is thenevacuated and the seals are made by heating the assembly therewithin byhigh frequency induction to a brazing temperature. The brazing materialfor making the seals may include 2% to 5% of titanium metal alloyed withtin, lead, copper, silver or gold, or alloys of these metals. Suchbrazing materials have a vapor pressure which permits brazing to besuccessfully carried out within. an evacuated space without the metalmigrating over the insulating surfaces and degrading the insulationbetween elements. After the parts have been brazed together and thejoints have solidified, air maybe released into the bell jar and thebell jar removed in order to release the completed tube for its intendedapplication. The general method of evacuating and sealing a metalenvelope tube within a bell jar. has previously been described in anapplication, Serial No. 94,380, filed May 20, 1946, by Mortimer E.Weiss, co-

inventor of the present application.

The form of invention which is shown in FIGURE 2 differs from thatpreviously described in that the anode disc has a deep depressed centralportion 11' and the grid disc 14 is dished toward the filament 26ratherthan away from the filament in order to decrease the interelectrodespacing as much as possible while at the same timeproviding an adequateinsulating path between elements. Also in this modification theeyelet-18 is provided around the periphery-of flange 17 with a turnedover edge 33 as an aid in obtaining the required accurately concentricarrangements of the electrodes, as weli as providing an exterior channelor gutter into which a brazing alloy may be placed. In this form-ofconstruction,

. anode disc 10, ceramic ring 12 and grid disc 14 may be bonded togetheras a separate step. We may thus join 1 these parts together with abrazing material which has a comparatively high vapor pressure by makingthe braze I 'in an atmosphere of hydrogen 'at sufficient pressure toprevent evaporation of the brazing material. The final sealbetween thecathode subassembly-and grid anode subwhich has a low vapor pressure. 7

A further modification of the present invention is shown in'FIGURE 6,wherein the ceramic ring 42 is H-sh aped in cross section, the channelsof the H'member being metallizecl'or tinned" before assembly. Ring 42 isaccurately ground to predetermine the anode to grid spac ing; The anodedisc in this form of construction includes a down turned rim' 44 whichdips into the upper with a brazing alloy.

' ode and said supports having extensions bearing againstmaterial cannotaffect the spacing between the electrodes. Furthermore, the walls of thechannels act as baffies to prevent the possibility of any materialevaporated from the brazing metal from depositing on the surface of theceramic, and thus reducing the resistance between the elements of thetube. The brazing material within the lower channel also serves toelectrically connect the cylindrical shell member 48 to the grid disc45. Alternatively, an additional conductor similar to conductors 21 maybe provided, passing through header disc 20 and electrically connectedto the grid disc 45. In this form of construction, it is preferable toreduce the diameter of grid disc 45 so that there is no possibility ofan electrical connection being formed between shield member 48 and thegrid disc 45. The shell member 43 then serves primarily only as a casingmember, though if electrical considerations warrant, it maybe groundedto serve as a shield.

While we have shown and particularly described several modifications ofthe present invention, it should be distinctly understood thatmodifications may be made Within the scope of the claims. Thus,additional grid elements may be employed by adding the required numberof grids and additional ceramic spacing discs, or a ceramic header maybe used instead of a glass header. Also, in-

f stead of a filamentary cathode, an indirectly heated cathode may besupported from lead-in conductors 21 to lie in close proximity to thegrid disc 14.

What is claimed is:

1 An electron discharge device including an anode disc and a grid disc,a ceramic spacer interposed between said discs-and hermetically sealedthereto, a tubular metal member having an insulating plug near one endand a number of lead-in wires passing through said plug, a cathodesupported within the other end of said tubular memher-adjacent said griddisc and said tubular member being hermetically sealed to said griddisc, said lead-in wires carrying supports for said cathode and'saidsupports having extensions bearing against said grid disc for spacingsaid cathode from said grid disc.

2. An electron discharge device including an anode disc and a grid disc,a ceramic spacer interposed between said discs and sealed thereto, atubular metal member having an insulating plug near one end and a numberof lead-in wires passing through said plug, a cathode supported withinthe other end of said tubular member and said tubular member beinghermetically sealed adjacent said spacer to said grid disc, said lead-inwires carrying supports for said cathode and said supports havingextensions bearing against said grid disc for spacing said cathode fromsaid grid disc.

3. An electron discharge device including an anode disc and a grid disc,a ceramic spacer ring interposed'between said discs, said discs beingbrazed to said spacer,

"a tubularmember having an insulating closure near one end and a numberof lead-in wires passing through said closure, a cathode adjacent saidgrid disc and supported Within the other end of said tubular member,said tubular member being hermetically sealed to said ceramic spacer,said lead-in Wires carrying supports for said cath- .saidgrid disc forspacing said cathode from said grid disc.

channel of the H, while the shell member 48" dips into the lower channelof the H. The spacing of the grid disc 45 from the anode 40 isdetermined by'the accurately ground heighth of the ring, while thespacing between the grid and cathode is determined as heretoforedescribed; 7 V ,The brazing metal within the annular channelshermetically seals the tube but variations in the amount of brazmg 4. Anelectron discharge device including an anode disc and a grid disc, aceramic spacer ring interposed between said discs, a.tubular metalmember having an insulating plug sealed near one end, a cathodesupported within the other end of said tubular member, said anode dischaving a turned down rim, said ceramic ring being H-shaped in crosssection and said rim extending into one channel of said ring, saidtubular member extending into the other channel of said ring saidcathode being spaced from said grid by support members carrying saidcathode and having extensions bearing against said grid disc.

5. An electron discharge device including an anode disc' and a griddisc, a ceramic spacer ring interposed between said discs, a tubularmetal member having an insulating plug sealed near one end, a cathodesupported Within the other end of said tubular member, said anode dischaving a turned down rim, said ceramic ring being H-shaped in crosssection and said rim extending into one channel of said ring, saidtubular member extending into the other channel of said ring and asealing material in said channels binding said rim and said tubularmember to said ring said cathode being spaced from said grid by supportmembers carrying said cathode and having extensions bearing against saidgrid disc.

6. An electron discharge device including an anode disc and a grid disc,a ceramic spacer ring interposed between said discs, a tubular metalmember having an insulating plug sealed near one end, a cathodesupported within the other end of said tubular member and adjacent saidgrid disc, said anode disc having a turned down rim, said ceramic ringbeing H-shaped in cross section and said rim being brazed in a channelof said ring, said tubular member being brazed in the other channel ofsaid ring the heighth of said ring determining the spacing between saidanode disc and said grid disc.

7. An electron discharge device including an anode disc and a grid disc,an apertured ceramic spacer ring interposed between said discs, atubular member having an insulating closure sealed near one end and anumber of lead-in wires passing through said closure, a cathodesupported Within the other end of said tubular member adjacent said griddisc, said anode disc having a turned down rim, said ceramic ring beingH-shaped in cross section and said rim being brazed in a channel of saidring, said tubular member being brazed in the other channel of saidring, tongued spacer members secured to some of said lead-in wires, thetongues of said spacer members fitting into apertures in said grid discand said spacer members carrying said cathode.

8. An electron discharge device including an anode disc and a grid disc,a ceramic spacer ring interposed between said discs, a tubular metalmember having an insulating plug sealed near one end, a cathodesupported within the other end of said tubular member, said anode dischaving a turned down rim, said ceramic ring being H-shaped in crosssection and said rim being brazed in a channel of said ring, saidtubular member being brazed in the other channel of said ring, tonguedspacer members supported within said tubular member, the tongues of saidspacer members fitting into notches in said grid disc and said spacermembers carrying said cathode.

9. An electron discharge device including an anode disc and a grid dischaving a central aperture therein, grid wires stretched across saidaperture, a ceramic spacer ring interposed between said discs and brazedthereto, a flanged tubular member having its flange brazed to said griddisc and an insulating plug sealed in said member remote from saidflange, a number of wires sealed through said plug, flat insulatingcathode supports secured to said wires, and having tongues resting innotches in the aperture in said grid disc and notches in said cathodesupports, and a cathode lying in said last mentioned notches.

10. An electron discharge device including an anode disc and a grid dischaving a central aperture therein,

grid wires stretched across said aperture, a ceramic spacer ringinterposed between said discs and brazed thereto, a flanged tubularmember having its flange brazed to said grid disc and an insulating plugsealed in said member remote from said flange, a number of Wires sealedthrough said plug, flat insulating cathode supports secured to saidwires and having tongues resting in notches in the aperture in said griddisc and notches in said cathode supports, and a filamentary cathodelying in said last mentioned notches.

11. An electron discharge device including an anode disc and a grid dischaving a central aperture therein, grid wires stretched across saidaperture, an insulating spacer ring interposed between said discs andsealed thereto, a flanged tubular member having its flange sealed tosaid grid disc and an insulating plug sealed in said member remote fromsaid flange, a number of wires sealed through said plug, flat insulatingcathode supports secured to said Wires and having tongues resting innotches in the aperture in said grid disc and notches in said cathodesupports, and a cathode lying in said last mentioned notches.

12. An electron discharge device including an anode disc and a griddisc, a ceramic spacer ring interposed between said discs, the thicknessof said ring determining the spacing between said anode disc and griddisc and said ring being sealed to said discs by means independent ofthe thickness of said discs, a tubular member having an insulatingclosure near one end and a number of leadin Wires passing through saidclosure, a cathode adjacent said grid disc and said tubular member beinghermetically sealed to said spacer, said lead-in wires carrying supportsfor said cathode.

13. An electron discharge device including an anode disc and a griddisc, a spacer ring interposed between said discs, a tubular metalmember having an insulating plug sealed near one end, a cathodesupported Within the other end of said tubular member, said anode dischaving a turned down rim, said ceramic ring being H-shaped in crosssection and said rim being sealed in a channel of said ring and flatfaces on said discs resting against the top and bottom of said ring todetermine the spacing therebetween, said tubular member being sealed inthe other channel of said ring.

14. An electron discharge device including an anode disc and anapertured grid disc, a ceramic spacer ring interposed between saiddiscs, a tubular member having an insulating closure sealed near one endand a number of lead-in wires passing through said closure, a cathodesupported within the other end of said tubular member adjacent said griddisc and tongued spacer members secured to some of said lead-in wires,the tongues of said spacer members fitting into apertures in said griddisc and said spacer members carrying said cathode.

References Cited in the file of this patent UNITED STATES PATENTS2,431,226 Berkey et a1. Nov. 18, 1947 2,446,765 Hickey et a1 Aug. 10,1948 2,459,859 Weston Jan. 25, 1949 2,462,921 Taylor Mar. 1, 19492,465,370 Glauber Mar. 29, 1949

